A real-gas equation of state uses two empirically determined constants, a and b, whose numerical values for three gases are listed below.
Gas
a (L2·atm·mol−2)
b (L·mol−1)
HF
2.50
0.030
H2O
5.46
0.030
Ar
1.36
0.032
One mole of each gas is placed in a 0.500 L rigid container at 200 K.
(a) Rank the three gases from lowest to highest actual pressure under these conditions. Justify your ranking in terms of the data in the table.
(b) Rank the three gases from smallest to largest actual molar volume when the external pressure is adjusted to 10.0 atm at 200 K. Provide reasoning that separates the influence of intermolecular attractions from that of molecular size.
(c) For HF and H2O, the constant b has the same value but a is markedly different. Explain, on the basis of molecular structure, why this occurs.